Manypeoplebelievetheglarefromsnowcausessnow-blindness.Yet,darkgl

Manypeoplebelievetheglarefromsnowcausessnow-blindness.Yet,darkglassesornot,theyfindthemselvessufferingfromheadachesandwateringeyes,andevensnow-blindness,whenexposedtoseveralhoursof"snowlight". TheUnitedStatesArmyhasnowdeterminedthatglarefromsnowdoesnotcausesnow-blindnessintroopsinasnow-coveredcountry.Rather,aman'seyesfrequentlyfindnothingtofocusoninabroadexpanseofbarrensnow-coveredterrain.Sohisgazecontinuallyshiftsandjumpsbackandforthovertheentirelandscapeinsearchofsomethingtolookat.Findingnothing,hourafterhour,theeyesneverstopsearchingandtheeyeballsbecomesoreandtheeyemusclesache.Natureoffsetsthisirritationbyproducingmoreandfluidwhichcoverstheeyeball.Thefluid coverstheeyeballinincreasingquantityuntilvisionblurs,thenisobserved,andtheresultistotal,eventhoughtemporary,snow-blindness. ExperimentsledtheArmytoasimplemethodofovercomingthisproblem.Scoutsaheadofamainbodyoftroopsaretrainedtoshakesnowfromevergreenbushes,creatingadottedlineastheycrosscompletelysnow-coveredlandscape.Eventhescoutsthemselvesthrowlightweight,darkcoloredobjectsaheadonwhichtheytoocanfocus.Themenfollowingcanthenseesomething.Theirgazeisarrested.Theireyesfocusonabushandhavingfoundsomethingtosee,stopscouringthesnow-blanketedlandscape.Byfocusingtheirattentionononeobjectatatime,themencancrossthesnowwithoutbecominghopelesslysnow-blindorlost.Inthiswaytheproblemofcrossingasolidwhiteterrainisovercome. Thescoutsshakesnowfromevergreenbushesinorderto_________.

A.give the men behind something to see

B.beautify the landscape

C.warm themselves in the cold

D.prevent the men behind from losing their way

正确答案是A